Ch. 3: Describing Sound Waves Flashcards
1
Q
Parameters describe features of a ____ ____
A
Parameters describe features of a sound wave
2
Q
The values of seven parameters are required to completely characterize a ____ ____
A
The values of seven parameters are required to completely characterize a sound wave
3
Q
The ____ of a sound wave is the ultrasound system and ____
A
The source of a sound wave is the ultrasound system and transducer
4
Q
Some parameters are determined by the ____ through which the ____ is traveling; The tissue is also called the ____
A
Some parameters are determined by the tissue through which the sound is traveling; The tissue is also called the medium
5
Q
Features of a sound wave:
A
- Definition
- Units
- Typical values
- Determined/established by
- Adjustable
- Formula/concept
6
Q
- 1 Cycle:
- 1 ____ and 1 ____
- The start of a ____ to the start of the next ____
A
- 1 Cycle:
- 1 Compression and 1 Rarefaction
- The start of a cycle to the start of the next cycle
7
Q
Period
- Definition— Period is the ____ it takes a wave to ____ a single ____, or the time from the start of one ____ to the start of the next ____
- Units— Period is reported in units of ____, such as ____ (µs), seconds, hours, or days
-
Typical values— The typical value of period in diagnostic ultrasound is ____ to ____ ____ (µs)
- This may also be written as:
- 6 x 10⁻⁸ to 5 x 10⁻⁷ seconds
- 0.06 to 0.5 µs
- 0.000 000 06 to 0.000 000 5 seconds
- This may also be written as:
- Determined by— Period is determined by the ____ only, not by the ____
- Adjustable— ____. The sonographer ____ change the period while using a basic ultrasound system with a particular transducer
- Formula— ____
A
Period
- Definition— Period is the time it takes a wave to vibrate a single cycle, or the time from the start of one cycle to the start of the next cycle
- Units— Period is reported in units of time, such as microseconds (µs), seconds, hours, or days
-
Typical values— The typical value of period in diagnostic ultrasound is 0.06 to 0.5 microseconds (µs)
- This may also be written as:
- 6 x 10⁻⁸ to 5 x 10⁻⁷ seconds
- 0.06 to 0.5 µs
- 0.000 000 06 to 0.000 000 5 seconds
- This may also be written as:
- Determined by— Period is determined by the sound source only, not by the medium
- Adjustable— No. The sonographer cannot change the period while using a basic ultrasound system with a particular transducer
- Formula— P = 1/f
8
Q
Frequency
-
Definition— Frequency is the ____ of particular events that occur in a specific duration of time
- For example, the frequency of presidential elections in the United States is 25 times per century
- The frequency of the menstrual cycle is 12 times per year
- In diagnostic sonography, the frequency of a wave is described as the number of ____ that occurs in ____ ____
- For example, the frequency of presidential elections in the United States is 25 times per century
-
Units— Frequency is reported in units ____ ____ , 1/second, ____ (Hz)
- Hertz is another way to say “____ ____ ”
- 1 cycle/second = 1 hertz
- 1,000 cycles/second = ____ ____
- 1,000,000 cycles/second = ____ ____
-
Typical values— In clinical imaging, frequency ranges from approximately ____ ____ to ____ ____
- Another way to say this is ____ ____ to ____ ____ per ____
- Determined by— Frequency of a sound wave is determined by the ____ only, not by the ____ through which the sound is traveling
- Adjustable— ____ . The sonographer ____ change the frequency while using a basic ultrasound system and transducer
- Formula— ____
A
Frequency
-
Definition— Frequency is the number of particular events that occur in a specific duration of time
- For example, the frequency of presidential elections in the United States is 25 times per century
- The frequency of the menstrual cycle is 12 times per year
- In diagnostic sonography, the frequency of a wave is described as the number of cycles that occurs in one second
- For example, the frequency of presidential elections in the United States is 25 times per century
-
Units— Frequency is reported in units per second, 1/second, Hertz (Hz)
- Hertz is another way to say “per second”
- 1 cycle/second = 1 hertz
- 1,000 cycles/second = 1 kHz
- 1,000,000 cycles/second = 1 MHz
-
Typical values— In clinical imaging, frequency ranges from approximately 2 MHz to 15 MHz
- Another way to say this is 2 million to 15 million per seconds
- Determined by— Frequency of a sound wave is determined by the sound source only, not by the medium through which the sound is traveling
- Adjustable— No. The sonographer cannot change the frequency while using a basic ultrasound system and transducer
- Formula— F = 1/P
9
Q
Frequency of infrasound:
A
Less than 20 Hz/0.02 kHz
10
Q
Frequency of audible sound:
A
Between 20 Hz/0.02 kHz and 20,000 Hz/20 kHz
11
Q
Frequency of ultrasound:
A
Greater than 20,000 Hz/20 kHz
12
Q
How did ultrasound get its name?
- ____ is classified based on the ability of humans to hear it
- If the ____ of a sound wave is less than ____ Hz, it is below the threshold of human hearing and cannot be heard
- That is, the sound is ____
- Sound waves with frequencies this low are defined as infrasonic or ____
- Humans can hear sound with frequencies between ____ Hz and ____ Hz
- This is called ____
- Sound with frequencies so high that humans ____ hear it is called ultrasonic or ____
- Ultrasound’s frequency is higher than ____ Hz (____ kHz)
A
How did ultrasound get its name?
- Sound is classified based on the ability of humans to hear it
- If the frequency of a sound wave is less than 20 Hz, it is below the threshold of human hearing and cannot be heard
- That is, the sound is inaudible
- Sound waves with frequencies this low are defined as infrasonic or infrasound
- Humans can hear sound with frequencies between 20 Hz and 20,000 Hz
- This is called audible
- Sound with frequencies so high that humans cannot hear it is called ultrasonic or ultrasound
- Ultrasound’s frequency is higher than 20,000 Hz (20 kHz)
13
Q
Why is frequency important in diagnostic sonography?
- Frequency is important in sonography because it affects ____ and ____ ____
- [Penetration— ____ ____]
- [Image quality— ____ ____]
- As frequency increases, penetration is ____, and image quality/detail is ____
- As frequency decreases, penetration is ____ ____, and image quality/detail is ____
A
- Frequency is important in sonography because it affects penetration and image quality
- [Penetration— How deep]
- [Image quality— Image resolution]
- As frequency increases, penetration is deeper, and image quality/detail is higher
- As frequency decreases, penetration is more shallow, and image quality/detail is less
14
Q
What is the Relationship between Frequency and Period?
- Period and frequency are ____ ____ to each other
- As frequency ____, period decreases
- As frequency decreases, period ____
- If one of these parameters remains constant, then the other remains ____
- Period and frequency have an even more special relationship that is called ____
- When two reciprocal parameters are multiplied together, the result is ____
- Period x Frequency = ____
- (The ____ it takes a wave to ____ a single cycle) x (the ____ of cycles that occurs in ____ second) = 1
- Use complimentary units:
- Seconds and ____
- ____ and kilohertz
A
What is the Relationship between Frequency and Period?
- Period and frequency are inversely related to each other
- As frequency increases, period decreases
- As frequency decreases, period increases
- If one of these parameters remains constant, then the other remains unchanged
- Period and frequency have an even more special relationship that is called reciprocal
- When two reciprocal parameters are multiplied together, the result is 1
- Period x Frequency = 1
- (The time it takes a wave to vibrate a single cycle) x (the # of cycles that occurs in 1 second) = 1
- Use complimentary units:
- Seconds and hertz
- Milliseconds and kilohertz
15
Q
More about Hertz
- Frequency is reported with units of ____
- Some people believe that hertz means “____ ____ ____”
- (1) Hertz means events per second
- (2) To which event are we referring?
- For example, what is the meaning of a sound wave with a frequency of 100 Hz?
- (1) 100 events occur each second
- (2) A cycle is our event. In this case, 100 Hz means 100 ____ per second
- What is the meaning of a flat-screen TV with a frame rate of 120 Hz?
- (1) 120 events occur each second
- (2) A frame is our event. Thus, the TV displays 120 frames per second
- What is the meaning of an individual with a heart rate of 1 Hz?
- (1) One event occurs each second
- (2) A heartbeat is the event. The individual’s heart contracts at a rate of 1 beat per second (or 60 beats per minute)
A
More about Hertz
- Frequency is reported with units of hertz (Hz)
- Some people believe that hertz means “cycles per second”
- (1) Hertz means events per second
- (2) To which event are we referring?
- For example, what is the meaning of a sound wave with a frequency of 100 Hz?
- (1) 100 events occur each second
- (2) A cycle is our event. In this case, 100 Hz means 100 cycles per second
- What is the meaning of a flat-screen TV with a frame rate of 120 Hz?
- (1) 120 events occur each second
- (2) A frame is our event. Thus, the TV displays 120 frames per second
- What is the meaning of an individual with a heart rate of 1 Hz?
- (1) One event occurs each second
- (2) A heartbeat is the event. The individual’s heart contracts at a rate of 1 beat per second (or 60 beats per minute)
16
Q
Three “Bigness” Parameters
- Three parameters describe the size, ____, or ____ of a sound wave:
- (1)
- (2)
- (3)
A
Three “Bigness” Parameters
- Three parameters describe the size, magnitude, or strength of a sound wave:
- (1) Amplitude
- (2) Power
- (3) Intensity
17
Q
Amplitude
-
Definition— Amplitude is the “____” of a wave
- It is the difference between the ____ value and the ____ or ____ value of an acoustic variable
- Amplitude is also the difference between minimum value and the ____ value of the ____ variable
-
Units— Amplitude can have units of any of the ____ ____
- Amplitude, in relative terms, can also be expressed in ____ (____)
- Typical values— In clinical imaging, pressure amplitude ranges from ____ ____ pascals (____) to ____ ____ pascals (____)
-
Determined by— Initially, amplitude is determined only by the ____, the ultrasound system
- However, amplitude decreases as sound propagates through the body
- The rate at which amplitude decreases as sound propagates depends on the characteristics of both the sound wave and the medium
- Adjustable— ____. A control system on a basic ultrasound system allows the sonographer to ____ initial amplitude of a wave
- Formula—
A
Amplitude
-
Definition— Amplitude is the “bigness” of a wave
- It is the difference between the maximum value and the average or undisturbed value of an acoustic variable
- Amplitude is also the difference between minimum value and the average value of the acoustic variable
-
Units— Amplitude can have units of any of the acoustic variables
- Amplitude, in relative terms, can also be expressed in decibels (dB)
- Typical values— In clinical imaging, pressure amplitude ranges from 1 million pascals (1 MPa) to 3 million pascals (3 MPa)
-
Determined by— Initially, amplitude is determined only by the sound source, the ultrasound system
- However, amplitude decreases as sound propagates through the body
- The rate at which amplitude decreases as sound propagates depends on the characteristics of both the sound wave and the medium
- Adjustable— Yes. A control system on a basic ultrasound system allows the sonographer to alter initial amplitude of a wave
- Formula—
18
Q
What is the difference between amplitude and peak-to-peak amplitude?
- Amplitude is measured from the ____, or undisturbed, value to the ____
-
Peak-to-peak amplitude is the ____ between ____ and ____ values of an acoustic variable
- Therefore, peak-to-peak amplitude is ____ the value of the amplitude
A
What is the difference between amplitude and peak-to-peak amplitude?
- Amplitude is measured from the middle, or undisturbed, value to the maximum
-
Peak-to-peak amplitude is the difference between maximum and minimum values of an acoustic variable
- Therefore, peak-to-peak amplitude is twice the value of the amplitude
19
Q
Power
-
Definition— Power is the ____ of energy ____ or the ____ at which ____ is performed
- Power, like ____, and ____, describes the “____” of a wave
- Units— Power have the unit of ____
- Typical values— In clinical imaging, typical powers range from ____ to ____ watts (____ to ____ milliwatts), depending on the diagnostic ultrasound technique
-
Determined by— Just like amplitude, initial power is determined by the ____, the ultrasound system
- Power ____ as sound propagates through the body
- The rate at which power ____ as sound propagates depends on the characteristics of the medium and the wave
- Adjustable— ____. Initial power, like amplitude, ____ be changed. A control on the ultrasound systems allows the sonographer to ____ the initial power of a wave
- Formula— ____
A
Power
-
Definition— Power is the rate of energy transfer or the rate at which work is performed
- Power, like amplitude, and intensity, describes the “bigness” of a wave
- Units— Power have the unit of watts
- Typical values— In clinical imaging, typical powers range from 0.004 to 0.090 watts (4 to 90 milliwatts), depending on the diagnostic ultrasound technique
-
Determined by— Just like amplitude, initial power is determined by the sound source, the ultrasound system
- Power decreases as sound propagates through the body
- The rate at which power decreases as sound propagates depends on the characteristics of the medium and the wave
- Adjustable— Yes. Initial power, like amplitude, can be changed. A control on the ultrasound systems allows the sonographer to alter the initial power of a wave
- Formula— Power ∝ Amplitude²
20
Q
How are amplitude and power related?
- Both amplitude and power are parameters that describe ____, or ____, of a wave
- When power increases, ____ ____ amplitude
- Similarly, when power decreases, amplitude ____
- Mathematically, power is ____ to the wave’s amplitude ____, The term is multiplied by itself
- Power ∝ Amplitude²
- [The symbol ∝ means proportional to]
A
How are amplitude and power related?
- Both amplitude and power are parameters that describe size, or magnitude, of a wave
- When power increases, so does amplitude
- Similarly, when power decreases, amplitude decreases
- Mathematically, power is proportional to the wave’s amplitude squared, The term is multiplied by itself
- Power ∝ Amplitude²
- [The symbol ∝ means proportional to]
21
Q
Intensity
-
Definition— Intensity is the ____ of energy in a sound beam
- To calculate intensity, divide the beam’s ____ by the beam’s ____-____ ____
- Intensity, like ____ and ____, describes the “____” of a wave
- Intensity relates to how the power in a wave ____ or is____ in space
- Therefore, intensity depends on both the ____ in the beam and the ____ over which the power is applied
- Units— The units of intensity are____/____ centimeter, or (____) (watts from ___ and ____ from beam area)
- Typical values— In clinical imaging, intensity ranges from ____ to ____ ____
-
Determined by— Just like ____ and____, initial intensity is determined only by the ____, the ultrasound system
- Intensity changes as sound propagates through the body
- The ____ at which intensity changes as sound propagates depends on the characteristics of both the sound wave and the medium
-
Adjustable—____. Initial intensity, like____ and____, ____ be changed
- A control on a basic ultrasound systems allows the sonographer to ____ the initial intensity of a wave
- Formula— ____
A
Intensity
-
Definition— Intensity is the concentration of energy in a sound beam
- To calculate intensity, divide the beam’s power by the beam’s cross-sectional area
- Intensity, like power and amplitude, describes the “bigness” of a wave
- Intensity relates to how the power in a wave spreads or is distributed in space
- Therefore, intensity depends on both the power in the beam and the area over which the power is applied
- Units— The units of intensity are watts/square centimeter, or W/cm² (watts from power and cm² from beam area)
- Typical values— In clinical imaging, intensity ranges from 0.01 to 300 W/cm²
-
Determined by— Just like amplitude and power, initial intensity is determined only by the sound source, the ultrasound system
- Intensity changes as sound propagates through the body
- The rate at which intensity changes as sound propagates depends on the characteristics of both the sound wave and the medium
-
Adjustable— Yes. Initial intensity, like power and amplitude, can be changed
- A control on a basic ultrasound systems allows the sonographer to alter the initial intensity of a wave
- Formula— I = P/A
22
Q
More About Intensity
- ____, ____, and intensity are three ____ that describe the ____ or strength of a ____
- These parameters tend to be____ related; Therefore, when intensity____, power and amplitude also____
A
More About Intensity
- Amplitude, power, and intensity are three parameters that describe the magnitude or strength of a wave
- These parameters tend to be directly related; Therefore, when intensity increases, power and amplitude also increase
23
Q
How is intensity related to power and amplitude?
- When discussing relationships between amplitude, power, and intensity, the word squared always follows the word ____
- Power is related to the amplitude ____
- Intensity is related to the ____ squared
- Power is related to the ____
A
How is intensity related to power and amplitude?
- When discussing relationships between amplitude, power, and intensity, the word squared always follows the word amplitude
- Power is related to the amplitude squared
- Intensity is related to the amplitude squared
- Power is related to the intensity
24
Q
Relationship between Intensity and Power
- Mathematically, intensity is ____ to power
- Intensity ∝ Power
- Examples:
- When a wave’s power is____, the intensity is doubled
- When a wave’s power is quartered, the intensity is ____
A
Relationship between Intensity and Power
- Mathematically, intensity is proportional to power
- Intensity ∝ Power
- Examples:
- When a wave’s power is doubled, the intensity is doubled
- When a wave’s power is quartered, the intensity is quartered
25
Q
Relationship between Intensity and Amplitude
- Mathematically, intensity is ____ to the wave’s ____ squared
- The term “squared” means that a number is multiplied by itself
- Intensity ∝ Amplitude²
- Examples:
- When a wave’s amplitude is doubled, the intensity increases to ____ times its original value
A
Relationship between Intensity and Amplitude
- Mathematically, intensity is proportional to the wave’s amplitude squared
- The term “squared” means that a number is multiplied by itself
- Intensity ∝ Amplitude²
- Examples:
- When a wave’s amplitude is doubled, the intensity increases to four times its original value
26
Q
Wavelength
-
Definition— Wavelength is the ____ or ____ of ____ complete cycle
- For example, imagine a sound wave as similar to a train; Wavelength is the length of a single boxcar in a train
- Units— Wavelength is measured in units of mm, meters, or any other unit of ____
- Typical values— In clinical imaging, wavelength in soft tissues ranges from ____ to ____ ____
-
Determined by— Wavelength is determined by ____*
- Wavelength is the ____ parameter that is determined by ____
- Wavelength is speed ____ by frequency
- Speed is determined by the ____ and is ____
- Frequency is determined by the ____
- Adjustable—____. The wavelength ____ be changed by the sonographer when using a basic ultrasound transducer
-
Formula— ____
- λ— ____ or ____
- c— ____
- f— ____
A
Wavelength
-
Definition— Wavelength is the distance or length of one complete cycle
- For example, imagine a sound wave as similar to a train; Wavelength is the length of a single boxcar in a train
- Units— Wavelength is measured in units of mm, meters, or any other unit of length
- Typical values— In clinical imaging, wavelength in soft tissues ranges from 0.1 to 0.8 mm
-
Determined by— Wavelength is determined by both the source and the medium*
- Wavelength is the only parameter that is determined by both
- Wavelength is speed divided by frequency
- Speed is determined by the medium and is constant
- Frequency is determined by the source
- Adjustable— No. The wavelength cannot be changed by the sonographer when using a basic ultrasound transducer
-
Formula— λ = c/f
- λ— lamba or wavelength
- c— speed
- f— frequency
27
Q
What is the difference between wavelength and period?
- Both wavelength and period describe a ____ cycle in a sound wave
- Wavelength refers to the ____ or ____ of a ____ ____
- Period refers to the ____ that it takes to complete a ____ ____
- Wavelength and period are differentiated by their ____ ; Wavelength has units of ____ , whereas period has units of ____
A
What is the difference between wavelength and period?
- Both wavelength and period describe a single cycle in a sound wave
- Wavelength refers to the length or distance of a single cycle
- Period refers to the time that it takes to complete a single cycle
- Wavelength and period are differentiated by their units; Wavelength has units of distance, whereas period has units of time
28
Q
What is the relationship between wavelength and frequency?
- As long as a wave remains in one ____, wavelength and frequency are ____ related
- As frequency increases, wavelength ____
- The lower the frequency, the ____ the wavelength
A
What is the relationship between wavelength and frequency?
- As long as a wave remains in one medium, wavelength and frequency are inversely related
- As frequency increases, wavelength decreases
- The lower the frequency, the longer the wavelength
29
Q
What is the wavelength of 1 MHz sound in soft tissue?
- In soft tissue, sound with a frequency of ____ ____ has a wavelength of ____ ____
A
What is the wavelength of 1 MHz sound in soft tissue?
- In soft tissue, sound with a frequency of 1 MHz has a wavelength of 1.54 mm
30
Q
What is the rule that defines the relationship between frequency and wavelength of sound in soft tissues?
- To find the wavelength of a sound wave in soft tissue, divide ____ ____ by the frequency in ____:
- wavelength (mm) = (____ ____/____) / ( frequency–____)
A
What is the rule that defines the relationship between frequency and wavelength of sound in soft tissues?
- To find the wavelength of a sound wave in soft tissue, divide 1.54 mm by the frequency in MHz:
- wavelength (mm) = (1.54 mm/µs) / ( frequency–MHz)
31
Q
Why is wavelength important in diagnostic ultrasound?
- Wavelength plays a very important role in ____ ____
- Shorter wavelengths are created by ____ frequency sound, This usually produces ____ quality images with ____ detail
- Sonographers should try to use ____ frequency transducers rather than ____ frequency transducers
A
Why is wavelength important in diagnostic ultrasound?
- Wavelength plays a very important role in image quality
- Shorter wavelengths are created by high frequency sound, This usually produces higher quality images with greater detail
- Sonographers should try to use higher frequency transducers rather than lower frequency transducers
32
Q
Propagation Speed
- Definition— Propagation speed is the ____ at which a sound wave travels through a ____
- Units— Speed is measured in units of ____ per ___, ____/µs, or any ____ divided by ____
- Typical values— In the body, the speed of sound ranges from ____ ____/____ to ____ ____/____, depending on the tissue through which it is traveling
-
Determined by— Speed is determined only by the ____ through which the sound is traveling
- Speed is not affected by the nature of the sound wave
- All sound, regardless of the frequency, travels at the same speed through any specific medium
- This means that sound with a frequency of 5 MHz and sound with a frequency of 3 MHz travel at the ____ propagation speed in the ____ medium
-
Adjustable—____. Speed of sound ____ be changed by the sonographer
- Speed ____ ____ when the wave travels from one medium to a different medium
- Speed is ____ in any given medium
- Formula— speed (m/s) = ____
A
Propagation Speed
- Definition— Propagation speed is the rate at which a sound wave travels through a medium
- Units— Speed is measured in units of meters per second, mm/µs, or any distance divided by time
- Typical values— In the body, the speed of sound ranges from 500 m/s to 4000 m/s, depending on the tissue through which it is traveling
-
Determined by— Speed is determined only by the medium through which the sound is traveling
- Speed is not affected by the nature of the sound wave
- All sound, regardless of the frequency, travels at the same speed through any specific medium
- This means that sound with a frequency of 5 MHz and sound with a frequency of 3 MHz travel at the same propagation speed in the same medium
-
Adjustable— No. Speed of sound cannot be changed by the sonographer
- Speed changes only when the wave travels from one medium to a different medium
- Speed is constant in any given medium
- Formula— speed (m/s) = frequency (Hz) x wavelength (m)
33
Q
What is the speed of sound in soft tissue?
- ____ m/s
- ____ mm/µs
- ____ km
A
What is the speed of sound in soft tissue?
- 1,540 m/s
- 1.54 mm/µs
- 1.54 km
34
Q
What is the speed of sound in biologic tissues other than soft tissue?
- Lung
- Fat
- Soft Tissue (average)
- Liver
- Blood
- Muscle
- Tendon
- Solid bone
A
What is the speed of sound in biologic tissues other than soft tissue?
- Lung– 500
- Fat– 1,450
- Soft Tissue (average)– 1,540
- Liver– 1,560
- Blood– 1,560
- Muscle– 1,600
- Tendon– 1,700 (1,850)
- Solid bone– 2,000 - 4,800
35
Q
What are the biologic tissues other than soft tissue from slow to fast?
A
- Lung
- Fat
- Soft Tissue
- Liver
- Blood
- Muscle
- Tendon
- Solid bone
36
Q
What are the biologic tissues other than soft tissue from fast to slow ?
A
- Solid bone
- Tendon
- Muscle
- Blood
- Liver
- Soft Tissue
- Fat
- Lung
37
Q
What is the speed of sound in other media?
- As a general rule, sound travels fastest in ____, slower in ____, and ____ in gases
- Solids have more particles, it is more ____
A
What is the speed of sound in other media?
- As a general rule, sound travels fastest in solids, slower in liquids, and slowest in gases
- Solids have more particles, it is more dense
38
Q
What is the speed of sound in air?
A
SPEED (m/s)
330
39
Q
What is the speed of sound in water?
A
SPEED (m/s)
1,480
